In order to meet demands from customers as well as for manufacturing purposes it has become increasingly important to provide sanitary napkins being as small and thin as possible, but still having advantageous absorbent properties. In order to provide such absorbent products, the absorbent layer of the product is often compressed before or during manufacture of the product.
Conventionally, the absorbent layer of thin sanitary napkins are provided in the form of a pre-compressed material roll, whereby the roll is cut to pieces of a suitable size, and the pieces are put into the absorbent product during manufacturing of the product. Such pre-compressed material in the form of a roll is normally expensive to provide, because of the need for external supply and a complex handling and manufacturing, due to e.g. the need of cutting unnecessary material during manufacturing, which also results in waste material. Thus, it would be beneficial if the formation and/or compression could be performed during manufacturing of the product.
The absorbent core(s), typically comprising one or more absorbent layer(s), normally comprises SAP-material, often consisting of particles having varying sizes, and typically a largest diameter size of about 850 μm. A problem in the art is that when an absorbent core or layer comprising SAP particles is compressed (whereby a compression roller having a distance between the rollers of typically about 250 μm is used) the SAP particles tend to clog to the compression rollers, thereby causing rupture of the core resulting in manufacturing process arrests. This is especially a problem in the field of absorbent products, wherein many individual products need to be produced in a short time using high manufacturing rates, and is normally not acceptable, not the least for cost reasons to and/or quality aspects. Partly, this problem appears to be a result of deformation or rupture of the SAP-particles, resulting in stickiness of the particles and as a result clogging to the compression rollers. This problem is even more often encountered in environments or in weather conditions having high air humidity, as is often the case e.g. during summer time in many areas.
One way to accomplish compression of a SAP-containing absorbent core without a resulting clogging, can be to provide a protection of tissue or nonwoven covering the SAP-particles. However, these materials are normally expensive, and the tissue material, for instance, typically has rather weak absorption properties. Also, using a covering sheet is complicated from a process point of view, since the edges of the covering material typically need to be cut, so that the tissue material does not extend outside the product sealing, which could result in leakage problems during use of the product.
From the prior art, WO00/10619, an absorbent product is disclosed comprising superabsorbent particles having anti-caking properties, in order to prevent the particles to adhere to manufacturing equipment. The anti-caking properties are provided by mixing SAP with inorganic powder, e.g. clay. However, these particles have not been used in connection with high density compression rollers.
Accordingly, there is a need in the art for an improved manufacturing process for manufacturing absorbent cores, thereby limiting the drawbacks and problems mentioned above, especially with regard to clogging of SAP-particles to compression rollers during manufacturing.
Thus, one object of the invention is to provide an absorbent core for use in an absorbent product, which core is compressed during manufacturing, and can be provided in a simpler and/or less expensive way than today, and which core further has absorbent properties that are acceptable and/or beneficial.